Wings not rendering even though it renders for other players

[Cheeky0wl]

My wings are not rendering when joining a server but still works as if i had wings. I checked the server console and it gives this whenever i Log in:

Netty Epoll Server IO #2/ERROR [minecraft/ArgumentTypes]: Could not serialize me.paulf.wings.server.command.WingsArgument@aacd069 (class me.paulf.wings.server.command.WingsArgument) - will not be sent to client!